IT Management

The “Holy Grail” of initialization messages is:

21.44.15 STC0035  +DFHSI1517  CICSPROD  Control is being given to CICS.

This message indicates CICS has fully initialized and sessions can be started. This entire process should only take a couple minutes, so if start-up is elongated, review the messages and time elapsed to diagnose the reason. If the start-up fails before this message appears, use the preceding instructions to access the publication messages and codes and find the failure message in the manual. Follow the instructions to fix the problem.

DFHSIT: The System Initialization Parameters

This is the most important of all CICS parameters. They establish the environment that this region will execute in for the life of the region. Many parameters establish and control CICS functions so their values are important. No two installations are the same, so these values should be reviewed regularly to determine their effectiveness.

A sample table is provided with each release since there may be new parameters and the contents may need to be changed. The sample contains defaults that are a starting point. (The sample is always provided as DFHSIT$$ and can be found in CICSTSnn.CICS.SDFHSAMP where nn is the release number.) An assembled version is also in CICSTSnn.CICS.SDFHAUTH since this is the only table that must run from an authorized library. You can use this version during early testing by installing a new release.

Under no circumstances should you use these defaults after early testing. One of the lessons most new systems programmers learn is that IBM’s defaults are notoriously not the values customers end up using. If you’re upgrading from a previous release, review the values in the previous release’s DFHSIT since they will probably be appropriate. The installation’s values for parameters such as APPLID, DFLTUSER, and SYSIDNT will likely have been established as standards.

Other parameters to review are storage sizes such as EDSALIM since the values may be inappropriate. There are several parameters covering Java Virtual Machine (JVM) settings; you can find those with JVM* as the prefix. Another “must change” parameter is AUXTR=OFF. This feature is mandatory for any problem determination; the auxiliary trace records now all go “above the bar” so the storage impact on the region is minimal. Some performance experts advise a value of OFF in a production region for overhead impact but beware; if you have any problems, you will be unable to see the trace of the problem and it will severely detract from your diagnosis.

The parameters also include suffixes for any other tables that the region may use. Although many of the previous tables are now resources that can be defined online, some may still be required. These suffixes must be identified in the corresponding DFHSIT parameter. The manual covering this topic is called the System Definition Guide (SC34-6999 for V4.1). Ensure that you have the correct release for your needs. Many of these parameters can be overridden, but the recommendation is to assemble a “standard” DFHSIT for regions and keep overrides to a minimum.

Messages and Codes: Your Best Tool!  

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